1. Field of the Invention
The present invention generally relates to the loading and unloading of vehicles, such as trucks and tractor trailers, parked at loading docks and, more particularly, is concerned with a vehicle restraining apparatus responsive to several different conditions which can arise due to the location of the rear of the vehicle relative to the restraining apparatus and which conditions necessitate that an alternative course of action be taken in restraining the vehicle at the loading dock.
2. Description of the Prior Art
Cargo is typically loaded onto and unloaded from vehicles, such as trucks and tractor trailers, while backed up to loading docks. Movement of the vehicle away from the dock while the loading or unloading operations are being performed can cause injury to workmen and damage to material handling equipment, such as forklifts, and to the cargo being handled.
Various ways have been employed heretofore to prevent inadvertent or premature movement of the vehicle. One way is to block or chock the wheels of the vehicle with wheel wedges or blocks. Another way is to use a cable or chain to secure the vehicle to the dock. Yet another way is to employ any of variety of vehicle locking devices mounted on the front of the dock or on the roadway in front of the dock. Various locking devices are disclosed in U.S. Pat. Nos. to Bickel (4,127,856), Grunewald et al., (4,146,888 and 4,267,748), Neff et al., (4,191,503), Hipp et al., (4,208,161 and 4,373,847), Hipp (4,264,259), Anthony et al., (4,282,621), Hahn et al., (4,379,354; 4,443,150 and 4,472,099), Metz (4,400,127 and 4,555,211), Bennett et al., (4,488,325), Ellis (4,553,895) and Hagen et al., (4,589,813). While the vehicle locking devices of those patents would seem to operate reasonably well and generally achieve their objectives under the range of operating conditions for which they were designed, most of those devices do not appear to adequately address the situation where the vehicle, for one reason or another, is not and sometimes cannot be locked by the device. Many of the devices purport to provide locking of the vehicle automatically so as to render chocking of the vehicle wheels unnecessary. However, wheel chocking may be the most readily usable vehicle restraint alternative in situations where securing of the vehicle by the locking device is not achieved for whatever reason.
Consequently, a need exists for a way to alert the dock attendant that locking of the vehicle has not been achieved and some alternative securement technique, such as chocking the wheels, should be employed.